If you have investigated a low-cost way to accumulate wealth, you have most expectedly landed on Fidelity’s fund program, and for justification. Fidelity was the first bulge bracket bank to launch mutual funds with a 0.00% management fee, and its more comprehensive index fund shelf now holds well over a trillion dollars in financial resources. But “low cost” does not pro grammatically mean “right for you.” This guide deconstructs every major index fund from Fidelity, breaks down the measurable distinction between the zero-fee ZERO funds and Fidelity’s broad-market index funds, and demonstrates how to choose and buy the one that actually fits your goals.
Comprehension Fidelity Index-Tracking Funds
A passive fund is an open-end fund, or ETF replicated a target market touchstone, such as the S&P 500 or the total U.S. stock market, rather than depending on a manager to pick constituent stocks. Because there is no discretionary stock selection, index-tracking funds generally carry far lower fees than manager-driven funds.
Fidelity offers two distinct categories of index funds:
- The ZERO family, proprietary funds with a 0.00% expense ratio, available only to Fidelity brokerage account holders.
- Traditional index funds, funds like FXAIX and FSKAX that track well-known, independently published indexes and charge a small but non-zero fee.
Both categories are legitimate, well-run options. The right one depends less on cost and more on how you plan to use the account.
Fidelity’s Zero-Fee Index Funds: The ZERO Family
Fidelity introduced its ZERO funds in 2018, and they remain the only index funds in the industry with a permanent 0.00% expense ratio. There are four of them.
FZROX: Fidelity ZERO Total Market Index Fund
FZROX monitors a Fidelity-proprietary index incorporating nearly 3,000 U.S. companies of all sizes, giving you large-, mid-, and small-cap allocation in an all-in-one fund. It is the closest ZERO equivalent to a “buy the whole U.S. market” strategy.
FZILX: Fidelity ZERO International Index Fund
FZILX furnishes vulnerability to cultivated and developing international markets outside the U.S., which is useful for investors who want global asset allocation without paying a minimum fee for it.
FNILX: Fidelity ZERO Large Cap Index Fund
FNILX monitors a Fidelity index of nearly 500 of the largest U.S. companies, interchangeable to an S&P 500 fund, though it is not authorized to use the S&P 500 name or rigorous protocol.
FZIPX: Fidelity ZERO Extended Market Index Fund
FZIPX covers mid- and small-cap U.S. companies, essentially the portion of the market left out of a large-cap fund like FNILX. It is often paired with FNILX to approximate total-market exposure.
Fidelity’s Traditional Low-Cost Index Funds
If the ZERO funds have no fee at all, why would anyone choose a fund that charges something? The answer comes down to portability and index licensing, covered in the next section, but first, the funds themselves.
FXAIX: Fidelity 500 Index Fund
FXAIX monitors the official S&P 500 Index and charges a management fee of 0.015%, or about $1.50 per year for every $10,000 allocated. It is one of the most heavily weighted funds in Fidelity’s full inventory and a foundation asset in retirement savings plans.
FSKAX: Fidelity Total Market Index Fund
FSKAX monitors the Dow Jones U.S. Broad Market Index, giving comprehensive market presence across large-, mid-, and small-cap U.S. equities. Like FXAIX, it carries a 0.015% management fee.
Both funds monitor autonomously sustained, registered reference indices rather than Fidelity’s self-constructed index, a differentiation that matters more than it might seem.
ZERO Funds vs. Traditional Index Funds: The Difference That Actually Matters
The headline difference between these two fund groups is not performance; long-term returns between FZROX and FSKAX, or between FNILX and FXAIX, have historically tracked each other closely. The real difference is portability.
ZERO funds are proprietary to Fidelity and generally cannot be transferred “in kind” to another brokerage if you ever move your account. You would typically need to sell the shares first, which can trigger a taxable event in a regular brokerage account. Traditional funds like FXAIX and FSKAX track widely available indexes and are more commonly transferable.
For a retirement account you plan to keep at Fidelity indefinitely, that distinction may not matter much. For a regular investment account, or if there is any possibility you will switch brokers down the road, it is worth deliberating the fee savings against the potential complication.
How to Choose the Right Fidelity Index Fund
There is no single “premium” index fund from Fidelity; the best choice depends on your account type, duration target, and how much asset dispersion you want in one fund.
- Want the simplest possible core holding? A single total-market fund (FZROX or FSKAX) gives blanket coverage in one purchase.
- Want a well-known S&P 500 touchstone? FXAIX tracks the official index and is the more transferable option.
- Building a three-fund portfolio? Pairing a large-cap or total-market fund with FZILX (international) and a bond index fund is a common, low-cost structure.
- Investing through a taxable account you may eventually move? Lean toward the traditional funds over the ZERO lineup.
How to Buy Index Funds From Fidelity
Buying an index fund from Fidelity is uncomplicated once you have an account open:
- Open a Fidelity investment account, IRA, or other approved account; there is no minimum subscription required for any of the funds referenced here.
- Use Fidelity’s Mutual Fund Search engine or ETF screener and filter by “Index” under governance framework.
- Search the fund by its market identifier (for example, FXAIX or FZROX) and evaluation its fund profile, portfolio, and management fee.
- Enter a dollar amount or share volume and execute the trade through your account or the Fidelity app.
- Consider setting up dollar-cost averaging (DCA) to build the position progressively through automatic recurring investments.
Vulnerabilities and Determinants
Index funds are not risk-free. Because they are designed to mirror the market, they will decline when the market declines, there is no manager attempting to limit losses. International funds like FZILX carry alternative currency and global macro risk. And while a 0.00% or 0.015% management fee is extraordinarily low, fees are only one part of aggregate return; portfolio diversification and time in the market generally matter more than marginally compressing yields off a fund’s cost.
This article is for reference purposes only and is not customized investment advice. Before investing in any fund, examine the offering circular for full strategic specificities, risks, charges, and expenses, and consider speaking with a Registered Investment Advisor (RIA) about your particular circumstances.
Conclusion
Fidelity has built one of the most aggressive index fund lineups in the industry, from the zero-fee ZERO funds to long-standing options like FXAIX and FSKAX. An optimal decision is not logically the one with the absolute lowest fee; it is the one that matches how you plan to use the account, how much risk distribution you need, and whether transferability to another account is something you will ever need. Start with your goals, compare the fund’s reference index and management fee, and build from there.